Four projects will be continued in this study. They are: 1) the isolation and reduction in size of the fragment of corynephage beta DNA that carries the gene for diptheria toxin, 2) characterization of plasmids associated with C. diptheriae and other corynebacteria, 3) initiation of DNA-DNA homology studies between various C. diptheriae biotypes and other corynebacteria, 4) examination of the anti-repressor or anti-inhibitor hypothesis as an explanation of the basis for the heteroimmune repression of the bin class of gamma mutants in strain C7 (beta).